Cotton—a natural fiber consisting of 90% cellulose—has been widely used for centuries. To expand its properties and use, numerous studies have since explored functionalizing cotton with different metal, semiconductor, organic, and carbon-based materials. Resulting hybrid cotton textiles exhibit enhanced properties and incorporate the unique mechanical, optical, and electrical properties of these systems. As examples, cotton/metal (Ag, Au, Cu, Pd, and Pt) composites possess conductive and/or catalytic properties useful in medical, photocatalytic, and electronic applications. Wide gap semiconductor functionalized cotton (e.g., with TiO2 or ZnO) shows good UV-blocking properties, exhibits self-cleaning behavior, and possesses antibacterial properties. Cotton textiles have been modified with carbon nanotubes to obtain features such as enhanced mechanical properties, flame retardation, and hydrophobicity.